The use of planetary gear systems in vehicular transmissions is well known in the vehicular art. In order to achieve a desired output speed from a vehicular transmission, the transmission will receive input from an engine and convert the imparted input energy to an output torque. Such a system will typically employ one or more planetary gear sets that may be connected between a torque converter and the output shaft of the transmission. Each planetary gear set includes a sun gear, a ring gear and a plurality of planet (or pinion) gears supported on a carrier operatively to connect the sun and ring gears. Various torque transfer devices in the nature of clutches and brakes are utilized in combination with the planetary gear sets to control the relative rotation of one or more components thereof and thereby produce the desired drive ratios.
In order to effect an operative connection between a torque transfer device in the nature of a brake or clutch with the planet gears, a reaction carrier may be employed. A typical reaction carrier is made up of a spider portion that is secured to a generally annular base portion. The base portion presents a plurality of circumferentially spaced, radially extending teeth to interact with a torque transfer device. A plurality of circumferentially spaced welding slots alternate with a plurality of planet or pinion support pin receiving bores. The spider portion comprises an annular deck with a plurality of circumferentially spaced legs extending substantially perpendicularly from the deck to be secured within the welding slots in the base portion. A plurality of circumferentially spaced planet or pinion support pin receiving bores alternate with the legs, and the pin receiving bores of the spider portion are disposed in register with an opposed support pin receiving bore in the base portion. A planet or pinion support pin, with a pinion gear rotatably mounted thereon, may be fitted into the opposed support pin receiving bores in the respective base and spider portions.
A reaction carrier having the foregoing construction provides a base portion that is normally stiffer than the top section. In other words, the pin receiving bores in the spider portion will be tangentially displaced to a greater degree than the pin receiving bores in the base portion when opposed forces or torques are applied to the reaction carrier--i.e.: when the forces applied to planet gears are opposed by the forces applied to the teeth on the base portion.
Thus, when an external torque or force is applied to the planetary gear set, the reaction carrier will multiply and transfer the torque to the sun gear, the ring gear and the pinion gears. Furthermore, the deflection of the reaction carrier caused by the torque, deforms the entire planetary gear system. Such deformation effects an inclination of the support pins on which the carrier gears are supported. Typically, this pin inclination, which results by relative tangential deflection of the opposed pin receiving bores, will cause one end of the support pins to deflect farther than the other end. Hence, one is faced with relative deflection or inclination of the support pins.
This unequal deflection by the two ends of the pinion supporting pins is the result of the fact that current reaction carrier designs are such that the interconnecting spider and base portions will have varying degrees of rigidity. Hence, a greater pin deflection occurs at the carrier portion that has less rigidity, which results in a non-zero, relative pin deflection--i.e.: pin inclination. Structural analysis shows that this undesirable pinion pin slope, during application of torque to the reaction carrier, is directly related to the local stiffness of the top and bottom sections of the reaction carrier assembly.
Even when one attempts to maximize the rigidity of the reaction carrier within reasonable size constraints, the aforementioned structural analysis further reveals that the pin slope is nevertheless greater than on the order of two tenths of a percent (0.2%). This two tenths of a percent deflection is enough to cause gear tooth misalignment between the pinion gears, the sun gear and the ring gear. As a result, undesirable gear tooth edge contact is made, which hastens the premature failure of gear teeth. Furthermore, gear tooth misalignment causes failure of the ring gear due to unexpected hoop stress. A further shortcoming of the present reaction carrier design is that the gear tooth misalignment will create vibration within the gear system resulting in added gear noise or grinding.
While attempts have heretofore been made to provide a reaction carrier assembly with structural properties that greatly reduce the relative deflection rate of the pinion support pin and the resulting gear tooth misalignment, there is a limit to which the structural strength of the reaction carrier components can be increased within acceptable weight, and size, limitations. As a result, the prior art has not provided a facile means or structural arrangement by which zero relative pin deflection (i.e.: zero pin inclination) can be achieved.